sedimentary
Chert (Jasper)
Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs), Color: Dark brown to black with tan inclusions, Luster: Waxy to dull, Crystal Structure: Trigonal (microscopic), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs), Color: Dark brown to black with tan inclusions, Luster: Waxy to dull, Crystal Structure: Trigonal (microscopic), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments. Often found as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools and weapons due to its sharp conchoidal fracture. Modern uses include jewelry (as jasper), aquarium stone, and as a durable material in road construction.
Geological facts
Chert has been used by humans for over 2 million years to make arrowheads and scrapers. Dark varieties are often referred to as flint.
Field identification & locations
Identify in the field by its hardness (it will scratch glass), its waxy texture, and its shell-like (conchoidal) fracture pattern when broken. Commonly found in riverbeds and coastal areas.
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